Running listDatabases command and renameCollection command concurrently on mobile storage engine can cause WriteConflict errors

The test that is being added as part of SERVER-34531 fails when run on the mobile storage engine due to WriteConflict errors that occur when concurrently running listDatabases and renameCollection. Obtaining the sizeOnDisk value is what appears to be causing the WriteConflict error. This section of listDatabases should be wrapped in a writeConflictRetry loop.